R33 Gtst Airbox Mod

[simpletool]

I thought I'd spend some time trying to improve the stock R33 GTST airbox.

I started the weekend by wanting to fix my pruning of the stock intake pipe when I fitted the FMIC years ago. One thing led to another and I ended up hacking up the stock box in an attempt to let more air in and reduce vacuum losses on the intake.

Parts:

Silicone sealant (high temp)

90mm PVC tube, 45degree bend

0.3mm aluminium flashing (plus some EFI hose for the edges)

The large scollop I cut into the stock intake pipe was sealed up with some 0.3mm aluminium flashing, massaging and silicon.

So now I've got 2 intakes for the stock airbox

I used the heat gun to turn the 90mmm PVC tube into a non-even rectangular shape so that it fit the tapering profile of the airbox lid. Then I cut a hole roughly 60mm high and 100mm wide and shoved it in with some silicone.

I angled the 45 degree bend down and flared out the intake as much as I could. I biased the intake so it would pull air from down and towards the guard (using the heat gun to make it soft, and work it again and again). I also have a cold-air feed angled up towards the intake fed from the spare hole from the stock SMIC return.

The intake can also draw air from behind the headlight virtually straight in. I put in a barrier between the airbox and the radiator made by sandwiching 2 layers of 0,3mm aluminium flashing to reduce hot air ingestion.

This is the view as seen from the cold-air feed (ie. looking up) which is a 2.5" silicone elbow. It looks pretty easy entry to me.

Result:

No idea. It seems to keep going stronger up top and have a bit more response but I can't say for sure it's not a placebo effect. The sound is a bit louder, especially the BOV. But it's nowhere near pod filter loud (which is good). So, my gut thinks it really has helped but who knows without dyno results. I did 107mph (pathetic I know!) at the drags a month ago - but that was with a dirty filter (K&N) - if I go back I'll see if it improves.

Background:

I looked into improving the stock airbox because it all looked a bit restrictive and there's a few results on here that indicate it's nowhere near as good as the GTR airbox (which itself improves by opening up the 2nd intake). I also had some problems with power dropping off after 6000rpm. But considering I only make 230rwkw @ 14psi I'm not expecting miracles. I also put some hose clamps around the silicon intake pipe I fitted a year ago to reduce any sucking closed.

Edited January 30, 2012 by simpletool

[GTSBoy]

It's a good effort. I did essentially this about 10 years ago to my R32. Opened up the triangular air inlet in front corner of airbox, heated and deformed 90mm PVC elbow and attached it at the hole. Cut 100mm hole in inner guard between airbox and headlight and dropped the 90mm pipe through to another elbow and heated bellmouth angled to brake duct. (FMIC made lots of room where SMIC used to be). Same results. Nice compressor noise, frightened a number of pedestrians. Little placebo effect on power/accel, but I'm sure that running cooler air to the engine is worthwhile in that respect anyway. I did this at the same time as making the metal turbo inlet, so was impossible to separate the various effects anyway.

[cherring]

I bought an airbox for my R32 Gtst, turned out to be an airbox for a 33, but still sits nice in that spot. So what I did was fibreglass up the intake on the side since the snorkel didn't fit past my cooler piping. Then cut the back of the snorkel and attach it to a hole I cut on the front of the airbox above the filter. This worked really well and during tuning proved to be no restriction as with the top popped off the airbox it made 1kw more. So I have a hole cut into the front, getting the coldest air I can from behind the headlight and stopping as much hot engine air as I can and having a nice enclosed air box. Win.

[AngryRB]

ive been thinking bout the filter/air intake for a while and it was suggested to put he filter down in the front bumper so that it is completely open to the outside air. Obviously the filter will need cleaning more often but really what do you guys think? theoretically i think its the best solution, rather than stuff around with a cold air box wouldnt it be better to just fit the filter outside the engine bay???

sorry to hijack thread

[hypergear]

Try this. I managed 315rwkws pump 98 with.

[Bond]

I did similar to Hypergear but cut my holes up near where the snorkel attaches (hard to see unless you look) and also put some holes in the snorkel itself as it seems to constrict inside. Definite improvement and brought back a missfire that i have now sorted. Have not been on a dyno though.

[simpletool]

Try this. I managed 315rwkws pump 98 with.

Bonnet open or closed? That could be pulling a lot of hot air.

FWIW the filter itself shouldn't be much of a restriction. K&N say 1.5inches of water at 450CFM for a perfectly clean filter. But if a bit dirty perhaps 10inches of water (0.5psi). Much more restriction would be present in the lid and scoop/s to it.

[KiwiRS4T]

Wot no snorkel? May as well leave the lid off. I like the OP's idea better. Some time ago I cut a hole in the front of the lid and ran a duct to behind the headlight. Thinking about runnng a duct from the vent where the smic used to be.

[simpletool]

ive been thinking bout the filter/air intake for a while and it was suggested to put he filter down in the front bumper so that it is completely open to the outside air. Obviously the filter will need cleaning more often but really what do you guys think? theoretically i think its the best solution, rather than stuff around with a cold air box wouldnt it be better to just fit the filter outside the engine bay???

sorry to hijack thread

I thought about this and even bought the necessary parts to do it - parts to add a 2nd pod filter into the base of the box. But in the end I though the panel filter could flow enough. I have a K&N pod with 2.5" mount and 2.5" metal intake pipe 45° bend sitting on the shelf. I was going to plug it into the bottom corner of the box and mount the pod just below the stock SMIC return hole.

I didn't bother as I thought it had more draw backs than benefits. ie. probably next to no benefits (maybe 1 rwkw) - but would help when the filter got dirty. Draw backs were: legalities, extra noise, possible water into filter, extra cleaning of filter due to road grime, hassles of mounting, worries of sealing effectiveness over time - don't want unfiltered air into engine, etc.

[joeyjoejoejuniorshabadoo]

Thinking about runnng a duct from the vent where the smic used to be.

that's what i have done, however it's a pod/box/cai arrangement

[cherring]

My alteration is this.

[SargeRX8]

I done something similar on my brothers car. I like the above idea with the fibreglass, looks more permanent and less DIY.

Tao, I thought in that test you were running the stock air box with no filter inside?

I still think the best thing is a shielded pod with similar idea, cold air intake.

[cherring]

I done something similar on my brothers car. I like the above idea with the fibreglass, looks more permanent and less DIY.

Tao, I thought in that test you were running the stock air box with no filter inside?

I still think the best thing is a shielded pod with similar idea, cold air intake.

I just need to get the surface smoother and repaint it.

[simpletool]

I done something similar on my brothers car. I like the above idea with the fibreglass, looks more permanent and less DIY.

Tao, I thought in that test you were running the stock air box with no filter inside?

I still think the best thing is a shielded pod with similar idea, cold air intake.

I was thinking there looked like no filter inside that airbox.

I'm going to paint mine matt black sometime soon so it looks less junkyard racer.

[Kris..]

I just grafted a snorkel from an r31 airbox on the front of the lid, looks stock

[GTSBoy]

Man, R33 airboxes have a dose of the gays compared to R32 ones.

[simpletool]

that's what i have done, however it's a pod/box/cai arrangement

I have a 2.5" silicone 90° bend shoved into the stock hole. Better still would be to use a 3" to 2.5" 90° reducer with a velocity stack shoved in the intake end.

ie.

velocity stack with 73mm ID (1.5mm walls) and 127mm bell mouth. Shove this into the 3" end, then elbow it up into the stock hole with 2.5" outlet (or cut a 3" outlet and don't reduce).

[simpletool]

Man, R33 airboxes have a dose of the gays compared to R32 ones.

Perhaps but they flow more.

[kosmo90]

My alteration is this.

Sorry off topic but that is an awsome idea swapping the intercooler pipes like that.

[cherring]

Sorry off topic but that is an awsome idea swapping the intercooler pipes like that.

I wish I could take credit for it, I bought the car that way, but I suspect it had this intercooler setup when it landed in the country.